Conventionally, in chairs used indoors, vehicle seats or the like, ones are often used, in which a cushion material or flexible pad is installed on a part thereof to be touched by a human body, such as a seat surface or a back rest, and then a surface thereof is covered with a cover material. Various structures are employed to fix the cover material. In order to fix and externally conceal the cover material, a structure is known, in which a wire as a to-be-locked member is arranged in a groove of a cushion material, cover-material fastening clips are arrayed on an end edge of the cover material, and then the clips are engaged with the wire, thereby fastening the cover material. Each of the clips has a chuck portion configured to be locked to a locking end of a locking end member attached to the cover material and a hook portion configured to be hooked and locked on the wire provided in the groove of the cushion material. In order to facilitate an operation of hooking the hook portion onto the wire, various shapes are proposed for the hook portion.
For example, a fastening clip disclosed in Patent Document 1 includes a chuck portion configured to be coupled to a hanging portion of a cushion cover and a hook portion configured to be hooked on a fastening wire in a hanging groove of a cushion pad. The hook portion has a claw-shaped hook piece and a guide piece arranged to oppose the hook piece. The guide piece is configured to cover an opening of the hook piece when the guide piece is in a free state, to be bent as the guide piece is pressed against the fastening wire, and then to return to the free state after the guide piece guides the fastening wire to a position, at which the fastening wire is hooked on the hook piece. The guide piece is shaped to extend toward the hook piece and is configured to be pressed and bent in a direction perpendicular to an extending direction thereof as the guide piece is pressed against the fastening wire.
Also, a cover-material fastening clip disclosed in Patent Document 2 is provided with a locking portion configured to be locked on a locking end member provided on an end edge of a cover material and a hook configured to be locked on a wire arranged in a cushion material. The hook is provided below the locking portion, and the hook is provided with an extension portion extending downward from the locking portion and a claw-shaped portion extending laterally from a distal end of the extension portion. The locking portion is provided with a wire guide piece. The wire guide piece extends downward from the locking portion and is provided with a bent portion in the middle thereof to be bent and extended toward a distal end portion of the claw-shaped portion. The wire guide piece is positioned such that a wire insertion opening narrower than a diameter of the wire is formed between the guide piece and the distal end portion of the claw-shape portion. When the cover-material fastening clip is locked on the wire, the wire insertion opening is pressed against the wire, and as a result, the wire guide piece and the extension portion or claw-shape portion of the hook are elastically deformed, thereby widening the wire insertion opening and thus allowing the wire to pass therethrough. After the wire passes through the wire insertion opening, the elastic deformation is restored so that the wire cannot pass therethrough back, thereby ensuring a reliable locking of the cover-material fastening clip.